In current aircraft propeller systems, a propeller fly ball overspeed governor is typically provided to limit the speed of the propeller. This hardware is used as a secondary propeller control mechanism independent from a primary mechanism, which may be a mechanical flyweight governor or an electro hydraulic control system. In order to protect the propeller from going below a minimum blade angle, auxiliary low pitch stop solenoid systems are also typically integrated in the Propeller Control Unit (PCU). These mechanisms however add weight, additional parts, and complexity to the PCU hardware.
In other applications, the propeller's feather valve is modulated to avoid overspeed. However, this method is only applicable to feather valves whose position can be controlled through bandwidth modulation of their command, e.g. to spring-loaded feather valves. This therefore imposes a certain hydraulic design to the PCU hardware.
There is therefore a need for improved aircraft propeller control system and methods.